Perfect binding is very popular because it is much faster and less expensive than side sewing or spine sewing, and it can be used to manufacture books which are too thick for saddle stitching. However, conventional perfect binding has the disadvantage that the pages are not held at the spine with the strength of sewn books. This, therefore, limits the categories of books to which perfect binding may be applied. Trade books and text books are a special category due to the expectations that they employ high quality, low opacity paper, requiring paper stock with low fiber content and heavy coatings. Adhesive binding of the such books becomes extremely difficult due to the requirement that these books must withstand rough handling and other abuses. Publishers of such books have generally considered it necessary to have them sewn for strength. This, however, adds greatly to the cost of such books and correspondingly limits the market for them.
Accordingly, a need has existed for many years for a method of binding books which is capable of producing books comparable in binding strength to books with sewn bindings but at the cost of perfect binding. The need, of course, has become more acute as both the cost of book manufacturing increases and level of competition in the publishing industry increases which requires stronger bindings at a lower cost. Moreover, a need exists for a method of binding books which is capable of binding both books of ordinary thickness as well as books having thicknesses as great as 4" (10.2 cm).